Young Vengeance
by Canis Lupus 54
Summary: Sasuke is transported to the Young Justice universe.
1. Chapter 1

"Enough," said Sasuke, cutting off another of Naruto's speeches, "I'm the strongest there is now."

Now, how to prove it? He could absorb the chakra of the captured bijuu, or he could use Kaguya's dimension switching technique. Their eyes were similar, after all.

 _Yes, that's it,_ he thought, _I'll prove my strength by mimicking the progenitor of all chakra._

So, he tried to shift to Kaguya's gravity dimension.

…

Aqualad's eyes widened in shock as the virtual air hockey puck slid into the goal. He glared at Kid Flash, his opponent, who was casually eating a banana during their match. M'gann and Robin watched with amusement.

"Recognized, Superboy, B04," the teleporter droned out.

With a flash of light, Superboy walked into the room, his face set in a scowl. M'gannn's face, meanwhile, lit up in a smile upon seeing him.

"Hi, Superboy," she said. "How was Metropolis?"

Superboy didn't answer, opting to walk through the holographic air hockey table, dispersing it in the process and causing M'gann to frown. The sound of a woman clearing her throat then echoed through the room, drawing the group's attention.

"Ready for training, everyone?" Black Canary asked as she and Martian Manhunter walked into the room.

"Uncle J'onn!" M'gann exclaimed, running up to the older Martian and wrapping him in a big hug.

"M'gann," Martian Manhunter said. "I was in the neighborhood, so I thought I'd stop by and see how you were adjusting."

"A few bumps, but I'm learning."

"That's all I can ask.

Superboy watched with envy, before turning and starting to walk away.

"Stick around," Black Canary called to him. "Class is in session."

Superboy stopped and turned to look at her.

Black Canary walked to the center of the room and a circle of light grew around her.

"Incoming signal," said the teleporter. "Not recognized. Action required."

Everybody in the room looked to the machine in shock for a moment. The announcement raised a million questions. Had the League's network been compromised? Who or what was coming? What was their intention? If they were headed for Mount Justice, did they know about the team?

Black Canary recovered first, assuming a fighting stance. "Override, Black Canary."

The teleporter whirred to life and a familiar flash of yellow light filled the room. When it faded, a teenage boy with pale skin and black hair, dressed in a grey zip-up shirt and a black skirt appeared. He looked around for a second, appearing profoundly confused, then his eyes settled on Canary. His eyes were bizarre, each had a unique design rendered in unusual colors, red, black, and purple.

"Koko wa doko?" the boy demanded in Japanese.

Most of the room's occupants simply looked confused, but Robin stepped in.

"Who are you? Why are you here?" he replied in Japanese.

"That's my line," the boy said coldly. "I appeared here after attempting to use some space-time ninjutsu."

Robin raised an eyebrow. Ninjutsu? Still, he got the gist of what the boy was saying. He gestured to the teleporter. "This machine makes artificial space-time ninjutsu. It must have intercepted whatever you did."

The boy scowled at Robin, causing the Boy Wonder and everyone else in the room to hallucinate a sword tearing through their throats. "Was this unintentional?"

Robin tried to appear unfazed, though sweat poured down his face. "Yes. We weren't even using the machine."

The boy's face relaxed slightly. "Send me back."

"My comrades don't speak this language. Let me see if they know what to do?" Robin said, then he turned to the other heroes and explained the situation in English. "The guy says he tried to use 'space-time ninjutsu,' must have resonated with the zeta tubes or something. Anyone know how to send him back?"

"Send him back?" Kid Flash exclaimed. "After the stunt he just pulled, he deserves some kind of punishment!"

"We need to know more."

"The zeta tubes only work between specific locations," Black Canary explained.

Robin turned back to the mysterious visitor. "We can't send you back with this machine, but we have other forms of transportation. Where are you from?"

"The Land of Fire," the boy replied. "I was right on the border of it, at the Valley of the End."

Robin did some quick searches on the computer. "I'm sorry, but those places don't exist."

The boy's eyes widened in surprise.

Superboy, who was fluent in Japanese thanks to the G-Gnomes that taught him, cut in. "Maybe he's from another planet."

"Another dimension is more likely," the boy said. "I might be able to send myself home, but given how my first attempt went, I'm not eager to try."

"Yo, Rob, fill us in," Wally complained.

"He's from another universe," Robin explained. "He says whatever technique got him here might be able to send him back, but apparently this wasn't where he was trying to come, so he's not eager to try it."

"Understandable," said Black Canary. "Who knows where he might end up if he tries again? We'll arrange for living conditions for him until he's ready to try again. He can even stay here, as long as he doesn't do that again."

Robin relayed the information to the boy and, tiring of this routine, had M'gann telepathically teach him English. The boy looked to Black Canary and his eyes shifted, becoming black.

"Thank you," the boy said. "I'm Sasuke Uchiha."

The others hesitantly introduced themselves.

"So, Sasuke, care to watch us train?" Canary asked.

"Sure."

Sasuke watched Canary easily defeat Kid Flash and Superboy. The woman wasn't half bad as a fighter. She was skilled, but lacked power. He pegged her at about genin level. The others were Academy student level. Superboy became angrier than he had already seemed after his defeat. The boy tried to storm off, but Black Canary stopped him.

"Training is mandatory," she explained.

A holographic screen suddenly appeared with Batman on it.

"Batman to the cave," he said. "Five hours ago, a new menace attacked Green Arrow and Black Canary. The attacker was capable of studying, then duplicating the abilities of its opponents. Arrow called for reinforcements, which nearly proved disastrous as our foe gained more and more power with each new combatant…"

Sasuke walked up to the screen and stuck his hand through it, widening his eyes in surprise when that actually worked. What sort of screen was this?

"Who is that?" Batman asked.

"I'll explain later," Robin said.

"…Anyway, it took eight Leaguers four hours to defeat and dismantle the android."

"An android?" Robin exclaimed. "Who made it? T.O. Morrow?"

"Good guess, Robin, but Red Tornado doesn't think so. The technology bears the mark of Professor Ivo."

"But Ivo's dead!" Aqualad protested.

"So we all thought, or hoped," said Canary.

"The parts are being sent to two separate STAR Labs facilities for study," Batman said. "We're also sending two decoy trucks. Your job is to protect the real trucks."

"So now we take out your trash?" Superboy demanded.

"You had something better to do?"

"Coordinates received," Aqualad said. "Let's go. Sasuke, you stay here."

The team moved out.

Sasuke waited for a few minutes before following the team out silently. He watched Robin and Superboy fail miserably at protecting the parts, then followed an enraged Superboy to Gotham. Superboy landed on a train. Sasuke leapt on next to him.

"Weren't you supposed to stay in the cave?" Superboy asked.

Sasuke merely grunted in reply and the two entered the train. They found Ivo inside with his mechanical monkeys, which Superboy destroyed in a rage.

"Access: Captain Atom," a dull voice said, then a yellow beam of energy hit Superboy in the chest, sending him flying backwards.

An android stepped out of the darkness. Ivo looked at Sasuke.

"Amazo, get him too," Ivo said.

Sasuke's eyes shifted to his Sharingan and Rinnegan, then he fired Amaterasu at the strange being before him. The sun heated flames quickly melted through the androids outer shell. Sasuke formed a partial Susanoo and bisected the android with his sword.

Ivo looked on in shock, then bolted for the door. Sasuke teleported between Ivo and the door and prepared a Chidori.

"Sasuke, wait!" Superboy yelled. "We don't kill the bad guys!"

Sasuke shrugged and made eye contact with Ivo, who screamed in pain and collapsed, unconscious.

…

"You both disregarded orders and jeopardized the mission," Batman said. "The end result worked out, but you're both going to have to learn to work with a team if you're going to be a part of this team."

Superboy looked at the floor. Sasuke just grunted.

"That said, good work. Sasuke, your welcome on the team. Just try some teamwork."

"I've been part of a team before," Sasuke said. "I think I'll adjust."


	2. Chapter 2

"Recognized: Kid Flash, B03."

A flash of yellow light filled the room, drawing the inhabitants' attention.

"The Wall-man is here!" Kid Flash announced, walking into the cave wearing a bathing suit and holding various beach supplies. "Now let's get this party start—"

Kid Flash tripped over nothing, sending his supplies all over the floor and his beach ball bouncing through the room. It narrowly missed Batman and Red Tornado, who looked at him seriously. The team, meanwhile gave him amused looks, except for Sasuke, who wasn't even looking.

"—ed," Kid Flash finished.

"Wall-man, huh?" said the green-clad girl standing next to Green Arrow. "Mm, I love the uniform. What, exactly, are your powers?"

"Um, who is this?"

"Artemis, your new teammate."

"Kid Flash, never heard of you."

Green Arrow stepped forward. "She's my new protégé."

"What happened to your old one?"

"Recognized: Speedy, B06."

"Well for starters, he doesn't go by 'Speedy' anymore. Call me Red Arrow."

"Roy!" Green Arrow exclaimed. "You look—"

"Replaceable."

"It's not like that, you told me you were going solo!"

"So why waste time finding a sub? Can she even use that bow?"

"Yes, she can," Artemis said.

"Who are you?" asked Kid Flash.

"I'm his niece."

"She's my niece."

"Another niece?" asked Robin.

"But she is not your replacement," Aqualad said to Red Arrow. "We have always wanted you on the team, and we have no quota on archers."

"And if we did, you know who we'd pick," said Kid Flash.

"Whatever Baywatch, I'm here to stay," said Artemis.

Red Arrow started to walk away.

"Enough drama," said Sasuke. "Why are you here?"

"Wait, who is this?" Red Arrow asked.

"Uchiha Sasuke."

"You need a codename," said Batman.

"Shinobi. Now why is Red Arrow here?"

"Dr. Serling Roquette," Red Arrow said.

"Nanorobotics genius and claytronics expert at Royal University in Star City," Robin said, pulling up some screens. "Vanished two weeks ago."

"Abducted two weeks ago. By the League of Shadows."

"You want us to rescue her from the Shadows?"

"Sweet!" said Kid Flash, fist bumping Robin.

"I already rescued her," said Red Arrow. "But she finished a weapon called the fog for the Shadows. She's trying to create a virus to neutralize it at the local high school's computer lab."

"You left her alone?" Green Arrow asked.

"She's safe enough for now."

"Then let's you and I keep her that way."

"Don't you want to take your new protégé?"

Batman put a hand on Green Arrow's shoulder. "You brought this to the team. It's their mission now, which means it's hers too."

"Then my job's done," said Red Arrow, then he walked over to the teleporter.

"Recognized: Speedy—"

"That's Red Arrow, B06, update."

Kid Flash shot Artemis a glare.

…

The team was with Dr. Roquette at the local high school.

 _Miss Martian, link us up,_ Aqualad thought. _I do not want the Shadows intercepting our comms._

 _Woah, this is weird,_ Artemis thought.

 _And distracting,_ Dr Roquette thought. _Coding a distributed algorithm virus on a kiddie computer with less RAM than a wrist watch is hard enough, now I have to hear teen think in my skull._

 _Lady, do you always complain when someone tries to help you?_ Kid Flash asked.

 _Enough bickering,_ Sasuke thought. _Finish the virus and find the fog._

 _I would have to go online—_

 _Then do it. We'll protect you._

Roquette typed in a few commands. _Tracking fog._

Outside, Superboy heard a rustling in the bushes around the school. He dismissed it and leapt over to the other side of the school, landing just behind Miss Martian.

 _Miss Martian, Dr. Roquette has located the fog,_ Aqualad thought. _Reconfigure the bioship so that Robin and Superboy can pursue._

Miss Martian summoned the bioship. Robin and Superboy jumped inside and flew off towards the fog's location.

While they were distracted, a masked assassin vaulted over the fence and snuck into the building.

Kid Flash noticed a shadow moving across the floor and pursued, only to trip on some balls on the floor, then get knocked out by a blow to the head. The masked assassin opened the door to the computer lab and threw a shuriken at Dr. Roquette, only for Sasuke to move between them and hold out a hand, sending the shuriken flying back at the assassin, faster than it had been thrown.

 _Keep working. I'll handle this amateur,_ Sasuke said mentally

The assassin ducked under the shuriken and rolled into the room, then stood, drawing a sai, and stabbing at Sasuke. Sasuke casually caught her by the wrist and kicked her in the stomach, sending her flying across the room and through the wall, knocking her unconscious.

Shortly afterwards, Roquette finished the virus. Robin and Superboy cut off the Shadows at a S.T.A.R. Labs facility and disabled the fog. The assassin, Cheshire, was arrested and sent to Belle Reve.

"Sasuke, excellent work," said Aqualad as they watched Cheshire being taken away. "A lot more would have been lost without you.

"Thanks, but learn how to take care of things yourselves," Sasuke said as a reply. "I shouldn't have to carry this team all the time."

Sasuke walked away.


End file.
